The STEM is being used to characterize the reassociated hexagonal bilayer structures obtained from fragments of the hemoglobins of Lumbricus, Tubifex, Arenicola, Amphitrite, Macrobdella and the chlorocruins of Myxicola and Eudistylia. The results of STEM measurements on the reassociated hexagonal bilayer structures have been compared with the proposed "bracelet" model of the quaternary structure of annelid hemoglobins and chlorocruins and support the model. In this model subunits D1 and D2 form a scaffolding or "bracelet" decorated with twelve complexes of subunits M and T. In this project the automatic mass program was helpful in recognizing intact top view and side view molecules and measuring masses of thousands of particles (Qabar, Stern, Walz, Jen-Ting, Timovich, Wall, Kapp & Vinogradov, J. Mol. Biol. 222:1109-29, 1991). Similar measurements have been performed on a number of other hemoglobins (Vinogradov, Sharm, Qabar, Wall, Westrick, Simmons & Gill, J. Biol. Chem. 266:13091-96, 1991). A protocol for isolation of earthworm hemoglobin from a live specimen with minimal purification has given molecules of extraordinary quality which we are considering as a new mass standard.